update: add user cascade

djangoldp_notification/models.py

@@ -10,7 +10,7 @@ from django.db import models
 from django.db.models.signals import post_save
 from django.dispatch import receiver
 from oidc_provider.models import Token
-from django.core.urlresolvers import NoReverseMatch
+from django.urls import NoReverseMatch
 
 from djangoldp.fields import LDPUrlField
 from djangoldp.models import Model
@@ -18,7 +18,7 @@ from djangoldp.permissions import InboxPermissions
 
 
 class Notification(Model):
-    user = models.ForeignKey(settings.AUTH_USER_MODEL, related_name='inbox')
+    user = models.ForeignKey(settings.AUTH_USER_MODEL, related_name='inbox', on_delete=models.deletion.CASCADE)
     author_user = LDPUrlField()
     object = LDPUrlField()
     type = models.CharField(max_length=255)